The present invention comprises a new and distinct cultivar of Rhododendron hybrid used as a rootstock known by the varietal name ‘Rhodunter 150’. The new variety was discovered in Ahrensburg, Germany. The new variety is the result of a planned breeding program between an unnamed and unpatented Rhododendron fortunei variety (female parent) and Rhododendron cv. ‘Cunningham's White’ (unpatented male parent). ‘Rhodunter 150’ exhibits leaves and flowers that are more similar to its female parent than to its male parent. Additionally, ‘Rhodunter 150’ exhibits more vigorous growth when compared to its male parent. Further, the new variety differs from both parents in its improved tolerance to lime. In fact, such improved lime tolerance (no Fe-deficiency symptoms on soils up to 6.9 pH) distinguishes the new variety from other Rhododendron varieties known to the breeder and satisfied the purpose of the breeding program. ‘Rhodunter 150’ has been trial and field tested and has been found to retain its distinctive characteristics and remain true to type through successive propagations.